Thermostat



E. J. DEARY Dec. 11, 1934.

THERMOSTAT 2 Sheets-Sheet 1 Filed May 8, 1934 a llrllillillllllrirn II n INVENTOR MEM A RNEY Dec. 11, 1934. 5 j DEARY 1,983,740

THERMOSTAT Filed May 8, 1934 2 Sheets-Sheet 2 [DH 4RD 1 DEAR) JNVENTOR BYMX A ORNEY Patented Dec. 11, 1934 UNITED STATES PATENT OFFICE THERMOSTAT Application May 8, 1934, Serial No. 724,541

Claims.

This invention relates particularly to thermostats such as used for automatic fire alarm and like purposes.

Special objects of the invention are to provide 5 a thermostat which will be quickly responsive to temperature change, positive in its action, of durable but relatively inexpensive construction, rugged in design, made up of units which can be readily assembled either for different tempera- 0 ture specifications, wiring or other requirements, of small size and neat appearance, so that it may be located in exposed places without impairing architectural features and which will be dependable in action and will indicate in a readily observable way the actual condition of the unit.

Other objects and the novel features of construction, combinations and relations of parts by which all objects are attained are set forth or will appear in the course of the following specification.

The drawings accompanying and forming part of the specification illustrate certain practical embodiments of the invention, but as such illustration is primarily for purposes of disclosure, it will be appreciated that the structure may be modified and changed in various ways all within the true intent and broad scope of the invention.

Fig. l is a side elevation of one of the thermostat units as made up for mounting on an outlet box of a conduit wiring system.

Fig. 2 is a front view of the unit illustrating its appearance on the face plate of the wall box.

Fig. 3 is an enlarged cross-sectional view of the unit showing the shell in this instance as carried by the circuit wires.

Fig. 4 is an interior view showing the movable and fixed contacts Within the shell as they appear after removal of the thin heat collecting cap or cover carrying the fuse spring.

, Fig. 5 is a view'of the back of the base plate 40 which carries the electric contacts, the attached circuit wires appearing in section.

Fig. 6 is an inside face view of the detached fuse cap.

Fig. 'l is a part sectional view similar to Fig. 3, illustrating the circuit closing action of the spring released by melting of the fuse rivets and showing the base in this instance as mounted on a wall or ceiling bracket.

Fig. 8 is a front view on a smaller scale of the device appearing in Fig. 7, and showing how the open fuse holes in the cap provide a quickly read indication that the unit has been fused.

The unit consists in general of a light thin shell 10, carrying the contactmechanism and a light thin relatively large area heat collecting cap or closure plate 11, carrying a fusibly held spring for actuating the contact mechanism.

The fuse spring is shown as a spring bar 12, having a bent under end portion 13, secured to the inner surface of the cap near the rim by triangularly placed permanent rivets 14, and the opposite end bent under at 15, and secured flat against the central portion of the cap by fusible alloy 16, extending in part through companion openings 17, in the cap and spring to form in effect the fusible rivets 18, headed over by flow of the metal, the outer faces of the parts thus secured together.

Thus with this construction, without loss of sensitivity or responsiveness, the spring is held retracted securely enough to resist mechanical strains such as might be occasioned by careless handling, but is always ready to let go instantly at the melting temperature of the particular alloy in that unit. In making up the fuse unit, the spring is held with the under bent portion 15, flat against the cap plate and with the openings therethrough in register with the openings in the cap. Under such conditions, the fuse alloy passing through the registered openings has a tendency to overflow the surfaces at opposite ends of the openings and hence naturally forms the fuse rivets described. These as pointed out, give additional mechanical strength without actually cutting down the instant temperature responsiveness of the device.

The fuse cap is shown secured to the shell by having a flange 19, at the rim of the same curled inward over an outwardly bent flange 20, at the rim of the shell. A special rotary bending or crimping tool may be used to accomplish this interlocking connection of the cap and shell and this particular form of connection imparts additional strength and rigidity to both shell and cap, enabling them to withstand mechanical shocks and blows, even though made of metal so thin as to be quickly susceptible to temperature changes.

The contact mechanism within the shell consists in the present disclosure of a spring switch arm 21, fixedly supported at one end and carrying a contact 22, at the free end for engagement with a stationary contact 23. This stationary contact and the fixed end of the contact spring are shown as carried by segment plates 24, 25,

having bent up arcuate perforated terminal lugs 32, 33, Figs. 3 and 5, through which the circuit wires 34, 35, are entered and preferably soldered as indicated at 36.

An insulating washer 37 is shown in Fig. 3, between the terminal plates and the back of the shell and the latter is shown as having a tubular hub or bushing 38, providing clearance between the soldered joints and the enclosing casing structure. The space so provided may be filled with a suitable insulating wax, such as indicated at 39,

which can be poured in through the back of the case to seal the parts in position therein.

The unit may be mounted in various ways. Thus as indicated in Fig. 3, it may simply be hung from the circuit wires 34, 35, this being a suitable method of support in damp and more or less inaccessible locations.

Figs. 1 and 2 illustrate the unit as secured on the face of a cover plate 40, of an ordinary outlet box, in which case the wires 34, 35, from the terminal plates may be brought back to binding screw terminals 34a, 35a, on the back of the face plate for connection with wires in the conduit system. I

In Figs. '7 and 8, the mounting consists of an arched strap bracket 41, riveted to the back of the case at 42, and having perforated ends 43, for mounting on a switch box, wall or other support.

The fused spring on the cap is designed to cooperate with the switch spring in any of the various possible relatively rotated positions of the two. In Fig. 3, with the releasable end of the fuse spring directly over the free end of the contact spring or in an exactly reversed position as in Fig; '7, with the free end of the fuse spring over an intermediate portion of the contact spring, the release of the fuse spring will have the effect of thrusting the contact spring intocircuit closing engagement with the fixed contact. In other angular relations, intermediate these two positions, where only an intermediate portion of the fuse spring can engage the contact spring, said fuse spring nevertheless is capable of effecting the closure of the circuit. This is accomplished by having the two springs long enough to engage at some intermediate point in all angular relations of the two and by giving the fuse spring enough movement to effect the circuit closing action by engagement of the springs in any such relations.

It follows from this that the fuse cap may be put on the shell without particular regard to the contact mechanism inside the same. This elimination of any need for assembling the parts in a special relation means a considerable saving in time and expense and also assures that the device will operate no matter in what angular relation the parts have been put together. The latter is of particular importance where replacements are made on the location, where a cap which has fused may be pulled off as by pliers or other tool and be replaced by a new fuse cap and in which cases, it would be diflicult if not impossible for an operator to make sure that one spring was aligned with the other. In putting on these new fuse caps, the edge of the cap may be curled or spun over the flange of the shell by a suitable hand tool constructed to roll the rim of the cap over the shell flange by a simple rotating movement.

In making such replacements, the same or a different temperature fusing cap may be substituted, since the internal switch mechanism in the shell need not be disturbed in making a change from n temperature fuse to another. This, it

will be realized, is a great manufacturing advantage, enabling the fuse caps to be made up for different temperature operations and then to be assembled as required with previouslymade up switch units in the shells.

Another important feature in the construction illustrated, is that the fuse spring is in no part of the electric circuit and is entirely free of current carrying requirements. It is insulated from the switch spring in the illustration by a sheath or tube of insulation 44, about the switch spring. Therefore, even when the fuse spring engages the switch spring, there is no current in the fuse spring.

The switch spring is shown as split lengthwise at its base end at 45, Fig. 4, and as having these split ends separately secured on the mounting plate by separate rivets 46. This allows the spring a maximum of elasticity and at the same time holds it rigidly in line over the stationary contact. 7 I

A small vent 47, is usually provided in the cap to equalize pressure at opposite sides and prevent sucking moisture into the casing through any slight crevices, for instances around the crimped edge, upon expansive and contracting movements of the cap acting as a diaphragm.

The cap may be painted or finished off in any suitable manner at the outside, so that the heads of the fuse rivets at 18, will not ordinarily be noticeable. This smoothness of appearance serves as an indication that the fuseis in working order. When however, the alloy melts, the fuse strip in springing away snaps any molten fuse metal out of the openings 17, leaving them as sharply defined holes, as in Figs. 7 and 8, visible as such at a considerable distance and hence serving as indications that the fuse has let go. This indicating feature is quite valuable where there may be a number of fuse units all in one line and in which case, a quick inspection will indicate at once which of a number of similar units has been set off. While a full two wire insulated open circuit unit has been here shown, it wil be understood that this may be modified to meet different regulations or requirements. Also it will be appreciated that various other changes may be made without departure from the true spirit and broad scope of the invention.

What is claimed is:

1. Ina thermostat of the character disclosed, a fuse spring, an exposed heat collector having an opening therethrough, said spring being bent into engagement with said exposed heat collector and having an opening registering with the opening in the heat collector and fusible material extending as a rivet through said aligned openings and whereby the presence of said rivet closing the openings indicates the restrained condition of the fuse spring and the absence of such rivet indicates a released condition of the fuse spring. I

2. A thermostat,-comprising a shell of light material having an outwardly turned edge flange, contact mechanism supported within said shell, a fuse cap of light thin material closing said shell and having an edge' flange turned inwardly over the outturned flange of the shell and a spring for actuating said contact mechanism fusedly restrained on said fuse cap, said spring and fuse cap having aligned openings and a rivet of fusible material extending through said openings in the fuse spring and cap and holding the restrained portion of the spring in flat engagement with thecap.

3. A thermostat of the character disclosed, comprising a cupped shell, a cap closing said shell, contact mechanism in the back portion of said shell and a bowed spring mounted on the cap and having a restrained portion fusibly held to said cap in position to actuate the contact mechanism in the shell.

4. A thermostat of the character disclosed, comprising a cupped shell, a cap closing said shell, contact mechanism in the back portion of said shell, a spring mounted on the cap and having a portion fusibly held to said cap in position to actuate the contact mechanism in the shell, said cap having a small vent for equalizing pressure inside the shell with that outside.

5. In a thermostat, a heat collecting mounting plate and a fuse spring having reversely bent opposite end portions in flat engagement with said heat collecting plate, means permanently securing one of said reversely bent end portions to said plate and fusible means releasably securing the opposite end reversely bent portion to said plate, said fusible means comprising a rivet of fusible material, the heat collecting plate and said reversely bent portion of the spring engaged therewith having registering openings receiving said fusible rivet.

6. In a thermostat, a mounting plate and a fuse spring having reversely bent opposite end portions, means permanently securing one of said reversely bent end portions to said plate and fusible means releasably securing the opposite end reversely bent portion to said plate, the permanently secured portion of said spring being near the rim of said plate and the releasably held portion being near the central portion of said plate.

7. In a thermostat, a mounting plate and a fuse spring having reversely bent opposite end portions, means permanently securing one of said reversely bent end portions to said plate and fusible means releasably securing the opposite end reversely bent portion to said plate, the releasably held portion of the spring and the plate having registering openings and the fusible material extending through said openings to exert the effect of a rivet holding the parts together.

8. A thermostat comprising a thin metallic shell having an outwardly flanged rim, a fuse cap flanged inwardly over said outwardly flanged rim, a fuse spring on the back of said cap having reversely bent end portions secured to said cap, one of said reversely bent end portions being permanently held and the other reversely bent end portion fusibly held, the latter by fusible material extending as a rivet fastening through adjoining portions of the spring and cap, a stationary contact in the shell, a contact spring for engagement with said stationary contact and extending across the central portion of the shell in position to be actuated by the contact spring in various angular relations of said fuse spring and contact spring and insulating material interposed between said contact spring and fuse spring.

9. A thermostat comprising a shell and a cap applied thereto, a contact spring in the shell extending as a lever across the central portion of the shell and a fusibly held spring on the cap extending as a lever across the center of the cap and thereby operable on the contact spring in various angular relations of the two.

10. In a thermostat, relatively movable and fixed contacts, said movable contact consisting of a spring lever split at one end, fastenings securing said split ends in position with the free end of the contact lever overstanding the fixed contact and a fusibly held spring lever positioned for engagement with the free end portion of said spring contact lever.

EDWARD J. DEARY. 

